Why does Shang He eat a single food for three meals to lose weight?

First of all, I don't agree with this method of losing weight, because this method of losing weight is obviously a single intake of some elements, which will lead to long-term malnutrition, so even if you lose weight, it will hurt your vitality and it is not easy to recover it, so my suggestion is to eat more vegetables, reduce staple food and exercise more, and wish you health.